Bede : Because Claudius had commanded all Jews to depart from Rome. Josephus narrates that this happened in the ninth year of Claudius. Suetonius the historian reports it in this way: Claudius expelled the Jews from Rome, as they were continually making disturbances at the instigation of Chrestus. Whether he meant to restrain and suppress the Jews making disturbances against Christ, or also wished to expel the Christians as related religious members, it is not at all clear. — Commentary on Acts John Chrysostom : "And having found a certain Jew named Aquila, of Pontus by birth, lately come from Italy"--for the greater part of his life had been passed there--"and Priscilla his wife, because that Claudius had commanded all the Jews to depart from Rome." For though it was in the reign of Nero that the war against the Jews was consummated, yet from the time of Claudius and thenceforward it was fanning up, at a distance indeed, so that, were it but so, they might come to their senses, and from Rome they were now driven as common pests. This is why it is so ordered by Providence that Paul was led thither as a prisoner, that he might not as a Jew be driven away, but as acting under military custody might even be guarded there. — Homily on Acts 39